1. Field of the Invention
The present invention relates to vertical seismic profiling (also known as VSP) data processing for analysis of subsurface formation structure, and in particular to computerized processing to generate vertical seismic profiling-common image gathers (also known as VSP-CMP) by wavefield extrapolation.
2. Description of the Related Art
Vertical seismic profiling has been used for detailed reservoir characterization. Vertical seismic profiling is based on seismic measurements from seismic sensors or geophones located in wellbores in response to seismic energy transmitted by sources from planned locations located on the surface. In vertical seismic profiling, the sensors in the wellbore are placed more closely than is the practice when surface seismic surveys are performed, with sensors at the earth's surface. Due to the closer sensor spacing in vertical seismic profiling, greater resolution detail is made available in the seismic data in order to analyze and characterize the reservoir.
However, so far as is known, the pre-stack elastic inversion and time-domain imaging methodologies available for vertical seismic profiling survey data have not been as fully developed as those available for surface seismic survey data. Consequently, the full extent of information present in vertical seismic profiling data has not been made available for analysis and evaluation of subsurface structure and formations.